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Updated: Jun 16, 2025
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Ratiometric Imaging of Extracellular pH in Dental Biofilms
Published on: March 9, 2016
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Triple-function carbon-based Ca2+ ion-selective pH ring microelectrode to study real-time bacteria-mediated
Partha S Sheet1, Suji Park1, Anh Tuan Nguyen1
1Department of Chemistry, Oregon State University, Corvallis, USA, 97331.
Analytica Chimica Acta
|August 18, 2024
Summary
This study reveals how Streptococcus mutans bacteria cause tooth decay by producing acid that demineralizes hydroxyapatite (HA). A new triple-function scanning electrochemical microscopy (SECM) tip monitored real-time pH and calcium ion changes during this process.
Area of Science:
- Biomaterials Science
- Microbiology
- Electrochemistry
Background:
- Pathogenic bacteria like Streptococcus mutans contribute to tooth decay by altering the local oral pH.
- Acid production by S. mutans leads to the demineralization of hydroxyapatite (HA), a key tooth mineral, by releasing calcium ions.
- Understanding bacteria-mediated demineralization is crucial for developing strategies against dental caries.
Purpose of the Study:
- To investigate the real-time, bacteria-mediated demineralization of hydroxyapatite (HA) using S. mutans.
- To develop and utilize a novel triple-function scanning electrochemical microscopy (SECM) tip for simultaneous pH and calcium ion monitoring.
- To elucidate the dynamic process of HA demineralization and subsequent remineralization in a bacterial biofilm context.
Main Methods:
- Cultivation of S. mutans biofilm on HA substrates for 7 days.
- Development of a triple-function SECM-compatible tip integrating potentiometric pH and Ca2+ ion-selective sensors.
- Real-time monitoring of pH and Ca2+ concentration changes at the biofilm-HA interface using the SECM tip.
Main Results:
- The triple-function SECM tip successfully monitored simultaneous pH and Ca2+ changes above the S. mutans biofilm.
- S. mutans acid production caused a significant pH drop (7.2 to 6.5) and released approximately 300 μM Ca2+ ions from HA.
- Observed Ca2+ precipitation at the biofilm surface, indicating HA corrosion from underneath, followed by pH recovery.
- A glass substrate showed no Ca2+ release or pH recovery, highlighting HA's specific role.
Conclusions:
- The developed triple-function SECM tip enables simultaneous monitoring of pH and Ca2+ dynamics, advancing the study of bacteria-mediated demineralization.
- This technique provides new insights into the complex mechanisms of hydroxyapatite corrosion by oral bacteria.
- The methodology holds potential for studying similar bacteria-mediated corrosion processes in biomedical and environmental applications.
